This invention relates to an apparatus for evaluating combustion from information on the air ratio, the temperature and other factors obtained from optical information on a sample of light emitted from the flame, a controller and a method for controlling the combustion, a detector and a method for detecting knocking in an internal combustion engine, a controller and a method for controlling combustion in an internal combustion engine, and a vehicle.
Many methods or systems have been disclosed in which various parameters of flame in an internal combustor, such as a boiler, a gas turbine combustor or the like, are detected and used for closed loop control to constantly maintain the flame in an optimum combustion condition. Specifically, methods of detecting light emitted from flame have been proposed. For example, with respect to internal combustion engines, Japanese Patent Laid-Open Nos. 57-108734 and 57-108735 disclose arrangements in which a quartz glass rod is disposed in a screw casing on the combustion side while an optical fiber is disposed at the opposite end to detect flame light. Japanese Patent Laid-Open No. 57-16384 discloses an apparatus relating to these detecting systems in which a center electrode is inserted into an axial center portion of the quartz glass rod and in which a screw casing portion is formed as an electrode opposite to ground to have the function of an ignition plug. Japanese Patent Laid-Open No. 61-54416 discloses a similar type of apparatus. Also, an example of a basic experiment in which flame light is sampled to obtain the air ratio by using an optical apparatus including a lens mirror and filters is described on page 3362 of the Theses of the Japan Society of Mechanical Engineering (Edition B), volume 52 (1986-9).
If knocking, which is specific abnormal combustion, takes place in an internal combustion engine, the temperature of a cylinder side wall of a piston side wall is increased and the engine is thereby damaged. It is therefore necessary to detect occurrence of knocking at an early stage with sufficient reliability and to operate the engine in an operation range immediately before the range in which knocking takes place. Various detection methods for effecting optimized combustion have therefore been proposed. For example, methods of detecting light of flame in the combustion chamber include a knocking detecting method disclosed in Japanese Patent Laid-Open No. 57-73646, in which a high-frequency optical signal generated in impulse waves formed when knocking occurs is detected. Japanese Patent Laid-Open No. 59-87249 discloses a combustion controller which samples light of flame, stores an optimum combustion state pattern signal obtained from the intensity of light emitted from the flame, compares a combustion state pattern obtained during operation with the optimum combustion state pattern, and controls the air ratio, the ignition timing and other factors so that the combustion state pattern during operation becomes equal to the optimum pattern. Similar conventional methods or apparatus are disclosed in Japanese Patent Laid-Open Nos. 61-217726 and 61-160577.
In the conventional methods or apparatus described above, light in the whole wavelength range is detected and information on the ignition time, the extinction time, the flame continuation time, the luminance and other factors can be thereby obtained, but physical quantities including the air ratio and the flame temperature cannot be obtained. The air ratio is the ratio Qr/Q.sub.0 of an actual amount of air Qr supplied for combustion of a certain amount of supplied fuel to a theoretical amount of air Q.sub.0 necessary for completely burning the certain amount of supplied fuel. These factors cannot be obtained because wavelengths having strong correlation with the air ratio and the flame temperature are not exclusively detected while the whole emission is sampled.
In addition, the problem of non-uniformity of the flow in the fuel-air supply line to the internal combustion engine is inevitable and the air ratio on the supply basis and the actual air ratio in the internal combustion engine therefore do not coincide with each other. Owing to the influence of the difference therebetween, the air ratio and so on cannot be obtained with accuracy if the intensity of light having a particular wavelength is simply measured to obtain the air ratio.
In general, the air ratio is conventionally set to a value equal to or slightly smaller than 1 to reduce NOx with priority in consideration of prevention of environmental pollution. However, the proportion of CO is thereby increased and CO in the exhaust gas is changed into CO.sub.2 by using a catalyst. Under this condition, the fuel utilization efficiency is reduced. In these circumstances, therefore, it is desirable to achieve combustion evaluation improved in accuracy.
The known optical apparatus composed of a lens mirror, filters and other components have designed without considering the method of application to internal combustion engines, and they are mere experimental apparatus.